Plasma processing apparatus

ABSTRACT

In a plasma processing apparatus of an exemplary embodiment, a radio frequency power source generates radio frequency power for plasma generation. A bias power source periodically applies a pulsed negative direct-current voltage to a lower electrode to draw ions into a substrate support. The radio frequency power source supplies the radio frequency power as one or more pulses in a period in which the pulsed negative direct-current voltage is not applied to the lower electrode. The radio frequency power source stops supply of the radio frequency power in a period in which the pulsed negative direct-current voltage is applied to the lower electrode. Each of the one or more pulses has a power level that gradually increases from a point in time of start thereof to a point in time when a peak thereof appears.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/752,376 filed Jan. 24, 2020, which is based on and claims the benefitof priority from Japanese Patent Application No. 2019-018833 filed onFeb. 5, 2019 and Japanese Patent Application No. 2019-236679 filed onDec. 26, 2019, the entire contents of which are incorporated herein byreference.

FIELD

Exemplary embodiments of the present disclosure relate to a plasmaprocessing apparatus.

BACKGROUND

A plasma processing apparatus is used in plasma etching on a substrate.The plasma processing apparatus is provided with a chamber, a substratesupport, and two radio frequency power sources. The substrate supportincludes a lower electrode. The substrate support is configured tosupport the substrate within the chamber. A gas is supplied into thechamber for plasma processing. In order to generate a plasma from thegas, radio frequency power is supplied from one of the two radiofrequency power sources. Further, radio frequency bias power is suppliedfrom the other of the two radio frequency power sources to the lowerelectrode. Such a plasma processing apparatus is disclosed in JapanesePatent Application Laid-Open Publication No. 2000-173993.

SUMMARY

In an exemplary embodiment, a plasma processing apparatus is provided.The plasma processing apparatus includes a chamber, a substrate support,a radio frequency power source, and a bias power source. The substratesupport has a lower electrode. The substrate support is configured tosupport a substrate in the chamber. The radio frequency power source isconfigured to generate radio frequency power to generate a plasma from agas in the chamber. The bias power source is electrically connected tothe lower electrode and configured to generate bias power for drawingions into the substrate support. The bias power source is configured toperiodically generate a pulsed negative direct-current voltage as thebias power. The radio frequency power source is configured to supply theradio frequency power as one or more pulses in a first period in whichthe pulsed negative direct-current voltage is not applied to the lowerelectrode. The radio frequency power source is configured to stop supplyof the radio frequency power in a second period in which the pulsednegative direct-current voltage is applied to the lower electrode. Theradio frequency power source is configured to generate the radiofrequency power such that each of the one or more pulses has a powerlevel that gradually increases from a point in time of start thereof toa point in time when a peak thereof appears.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, exemplaryembodiments, and features described above, further aspects, exemplaryembodiments, and features will become apparent by reference to thedrawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a plasma processing apparatusaccording to an exemplary embodiment.

FIG. 2 is a diagram showing a configuration of a radio frequency powersource and a bias power source of a plasma processing apparatusaccording to an exemplary embodiment.

FIG. 3 is an exemplary timing chart of radio frequency power, iondensity, an electron temperature, and bias power.

FIG. 4A is a diagram showing an example of a waveform of combined powerof a plurality of power components, FIG. 4B is a diagram showing a powerspectrum of the combined power shown in FIG. 4A, and FIG. 4C is adiagram showing a waveform of radio frequency power HF of an example.

FIG. 5A is a diagram showing an example of a waveform of combined powerof a plurality of power components, FIG. 5B is a diagram showing a powerspectrum of the combined power shown in FIG. 5A, and FIG. 5C is adiagram showing a waveform of radio frequency power HF of an example.

FIG. 6 is a diagram schematically showing a plasma processing apparatusaccording to another exemplary embodiment.

FIG. 7 is a diagram showing a configuration of a radio frequency powersource and a bias power source of a plasma processing apparatusaccording to another exemplary embodiment.

FIG. 8 is another exemplary timing chart of radio frequency power, iondensity, an electron temperature, and bias power.

FIG. 9 is still another exemplary timing chart of radio frequency power,ion density, an electron temperature, and bias power.

FIG. 10 is still another exemplary timing chart of radio frequency powerand bias power.

FIG. 11 is a diagram showing a configuration of a radio frequency powersource according to another exemplary embodiment.

DETAILED DESCRIPTION

Hereinafter, various exemplary embodiments will be described.

In an exemplary embodiment, a plasma processing apparatus is provided.The plasma processing apparatus includes a chamber, a substrate support,a radio frequency power source, and a bias power source. The substratesupport has a lower electrode. The substrate support is configured tosupport a substrate in the chamber. The radio frequency power source isconfigured to generate radio frequency power to generate a plasma from agas in the chamber. The bias power source is electrically connected tothe lower electrode and configured to generate bias power for drawingions into the substrate support. The bias power source is configured toperiodically generate a pulsed negative direct-current voltage as thebias power. The radio frequency power source is configured to supply theradio frequency power as one or more pulses in a first period in whichthe pulsed negative direct-current voltage is not applied to the lowerelectrode. The radio frequency power source is configured to stop supplyof the radio frequency power in a second period in which the pulsednegative direct-current voltage is applied to the lower electrode. Theradio frequency power source is configured to generate the radiofrequency power such that each of the one or more pulses has a powerlevel that gradually increases from a point in time of start thereof toa point in time when a peak thereof appears.

In the second period in which the pulsed negative direct-current voltageis applied to the lower electrode, the ions are accelerated from theplasma toward the substrate, and thus etching of the substrate occurs.Therefore, in the second period, a reaction product is released from thesubstrate. In a case where the electron temperature of the plasma ishigh, re-dissociation of the reaction product occurs. The substancegenerated by the re-dissociation of the reaction product may bedeposited on the substrate. In the embodiment described above, since theradio frequency power is not supplied in the second period, the electrontemperature of the plasma is low in the second period. Therefore,according to the embodiment described above, the re-dissociation of thereaction product is suppressed. Further, in the first period in whichthe pulsed negative direct-current voltage is not applied to the lowerelectrode, the radio frequency power is supplied as one or more pulses.The power level of each of the one or more pulses gradually increases tothe peak thereof. Therefore, overshoot of the electron temperature issuppressed. As a result, according to the embodiment described above,excessive dissociation of a gas is suppressed.

In an exemplary embodiment, the plasma processing apparatus may furtherinclude a controller configured to control the bias power source to seta phase of a cycle of the pulsed negative direct-current voltage.According to this embodiment, it becomes possible to adjust a timedifference between the point in time of end of the supply of one or morepulses and the point in time when the application of the pulsed negativedirect-current voltage to the lower electrode is started. Therefore, itis possible to adjust the electron temperature of the plasma before theapplication of the pulsed negative direct-current voltage to the lowerelectrode is started.

In an exemplary embodiment, the controller may further control the biaspower source to set a duration length of the pulsed negativedirect-current voltage. According to this embodiment, it becomespossible to adjust a time difference between the point in time of end ofthe application of the pulsed negative direct-current voltage to thelower electrode and the point in time when the supply of the one or morepulses is started.

In another exemplary embodiment, a plasma processing apparatus is alsoprovided. The plasma processing apparatus includes a chamber, asubstrate support, a radio frequency power source, and a bias powersource. The substrate support has a lower electrode. The substratesupport is configured to support a substrate in the chamber. The radiofrequency power source is configured to generate radio frequency powerto generate a plasma from a gas in the chamber. The bias power source iselectrically connected to the lower electrode and configured to generatebias power for drawing ions into the substrate support. The bias powersource is configured to generate radio frequency bias power as the biaspower. The radio frequency power source is configured to supply theradio frequency power as one or more pulses in a first period in whichthe radio frequency bias power which is output from the bias powersource has a positive voltage. The radio frequency power source isconfigured to stop the supply of the radio frequency power in a secondperiod in which the radio frequency bias power which is output from thebias power source has a negative voltage. The radio frequency powersource is configured to generate the pulsed radio frequency power suchthat each of the one or more pulses has a power level that graduallyincreases from the point in time of start thereof to the point in timewhen a peak thereof appears.

In the second period in which the radio frequency bias power which isoutput from the bias power source has a negative voltage, the ions areaccelerated from the plasma toward the substrate, and thus etching ofthe substrate occurs. Therefore, in the second period, a reactionproduct is released from the substrate. In a case where the electrontemperature of the plasma is high, re-dissociation of the reactionproduct occurs. The substance generated by the re-dissociation of thereaction product may be deposited on the substrate. In the embodimentdescribed above, since the radio frequency power is not supplied in thesecond period, the electron temperature of the plasma is low in thesecond period. Therefore, according to the embodiment described above,the re-dissociation of the reaction product is suppressed. Further, inthe first period in which the radio frequency bias power which is outputfrom the bias power source has a positive voltage, the radio frequencypower is supplied as one or more pulses. The power level of each of theone or more pulses gradually increases to the peak thereof. Therefore,overshoot of the electron temperature is suppressed. As a result,according to the embodiment described above, excessive dissociation of agas is suppressed.

In an exemplary embodiment, the plasma processing apparatus may furtherinclude a controller configured to control the bias power source to seta phase of the radio frequency bias power. According to this embodiment,it becomes possible to adjust a time difference between the point intime of end of the supply of the one or more pulses and the point intime when the potential of the lower electrode has a negative peak.

In an exemplary embodiment, a rise time of each of the one or morepulses may be longer than a minimum rise time of a pulse of radiofrequency power capable of being output from the radio frequency powersource.

In an exemplary embodiment, the radio frequency power source may includea power generator and an output. The power generator is configured togenerate the radio frequency power. The output is configured to outputthe radio frequency power generated by the power generator.

In an exemplary embodiment, the radio frequency power which is generatedby the power generator includes a plurality of power components. Theplurality of power components have a plurality of frequencies,respectively. The plurality of frequencies are set symmetrically withrespect to a fundamental frequency at an interval of a predeterminedfrequency. An envelope of the radio frequency power has a peak thatperiodically appears at a time interval which is defined by thepredetermined frequency or a frequency that is a multiple of twice ormore the predetermined frequency. A power level of the radio frequencypower is set to be zero in a period excluding a period between azero-cross region of the envelope immediately before a point in time ofappearance of each of the peaks and a zero-cross region of the envelopeimmediately after the point in time of the appearance.

In an exemplary embodiment, the power generator may include a waveformdata generator, a quantize, an inverse Fourier transformer, and amodulator. The quantizer is configured to quantize waveform datagenerated by the waveform data generator to generate quantized data. Theinverse Fourier transformer is configured to generate I data and Q databy applying inverse Fourier transform to the quantized data. Themodulator is configured to generate a modulated radio frequency signalby modulating two reference radio frequency signals of which phases aredifferent from each other by 90° by using the I data and the Q data. Inthis embodiment, the power generator is configured to generate the radiofrequency power from the modulated radio frequency signal.

In an exemplary embodiment, the power generator may further include anamplifier configured to amplify the modulated radio frequency signal togenerate the radio frequency power.

In an exemplary embodiment, the radio frequency power source may beconfigured to be capable of adjusting a rise time of each of the one ormore pulses.

In an exemplary embodiment, the radio frequency power source may beconfigured to sequentially supply a plurality of pulses as the one ormore pulses in the first period.

Hereinafter, various embodiments will be described in detail withreference to the drawings. In the drawing, the same or equivalentportions are denoted by the same reference symbols.

FIG. 1 is a diagram schematically showing a plasma processing apparatusaccording to an exemplary embodiment. A plasma processing apparatus 1shown in FIG. 1 is a capacitively coupled plasma processing apparatus.The plasma processing apparatus 1 is provided with a chamber 10. Thechamber 10 provides an internal space 10 s therein.

The chamber 10 includes a chamber body 12. The chamber body 12 has asubstantially cylindrical shape. The internal space 10 s is providedinside the chamber body 12. The chamber body 12 is formed of, forexample, aluminum. A film having corrosion resistance is provided on theinner wall surface of the chamber body 12. The film having corrosionresistance may be a film formed of ceramic such as aluminum oxide oryttrium oxide.

A passage 12 p is formed in the side wall of the chamber body 12. Asubstrate W passes through the passage 12 p when it is transferredbetween the internal space 10 s and the outside of the chamber 10. Thepassage 12 p is made to be able to be opened and closed by a gate valve12 g. The gate valve 12 g is provided along the side wall of the chamberbody 12.

A support 13 is provided on a bottom portion of the chamber body 12. Thesupport 13 is formed of an insulating material. The support 13 has asubstantially cylindrical shape. The support 13 extends upward from thebottom portion of the chamber body 12 in the internal space 10 s. Thesupport 13 supports a substrate support 14. The substrate support 14 isconfigured to support the substrate W in the internal space 10 s.

The substrate support 14 includes a lower electrode 18 and anelectrostatic chuck 20. The substrate support 14 may further include anelectrode plate 16. The electrode plate 16, the lower electrode 18, andthe electrostatic chuck 20 are provided in the chamber 10. The electrodeplate 16 is formed of a conductor such as aluminum, for example, and hasa substantially disk shape. The lower electrode 18 is provided on theelectrode plate 16. The lower electrode 18 is formed of a conductor suchas aluminum, for example, and has a substantially disk shape. The lowerelectrode 18 is electrically connected to the electrode plate 16.

The electrostatic chuck 20 is provided on the lower electrode 18. Thesubstrate W is placed on the upper surface of the electrostatic chuck20. The electrostatic chuck 20 has a main body and an electrode. Themain body of the electrostatic chuck 20 has a substantially disk shapeand is formed of a dielectric. The electrode of the electrostatic chuck20 is a film-shaped electrode and is provided in the main body of theelectrostatic chuck 20. The electrode of the electrostatic chuck 20 isconnected to a direct-current power source 20 p through a switch 20 s.When the voltage from the direct-current power source 20 p is applied tothe electrode of the electrostatic chuck 20, an electrostatic attractionforce is generated between the electrostatic chuck 20 and the substrateW. Due to the generated electrostatic attraction force, the substrate Wis attracted to the electrostatic chuck 20 and held by the electrostaticchuck 20.

A focus ring FR is mounted on a peripheral edge portion of the substratesupport 14. The focus ring FR is provided in order to improve thein-plane uniformity of plasma processing on the substrate W. The focusring FR is substantially plate-shaped and annular. The focus ring FR maybe formed of silicon, silicon carbide, or quartz, but not limitedthereto. The substrate W is disposed on the electrostatic chuck 20 andin a region surrounded by the focus ring FR.

A flow path 18 f is provided in the interior of the lower electrode 18.A heat exchange medium (for example, a refrigerant) is supplied from achiller unit 22 provided outside the chamber 10 to the flow path 18 fthrough a pipe 22 a. The heat exchange medium supplied to the flow path18 f is returned to the chiller unit 22 through a pipe 22 b. In theplasma processing apparatus 1, the temperature of the substrate W placedon the electrostatic chuck 20 is adjusted by the heat exchange betweenthe heat exchange medium and the lower electrode 18.

The plasma processing apparatus 1 is provided with a gas supply line 24.The gas supply line 24 supplies a heat transfer gas (for example, Hegas) from a heat transfer gas supply mechanism to the gap between theupper surface of the electrostatic chuck 20 and the back surface of thesubstrate W.

The plasma processing apparatus 1 further includes an upper electrode30. The upper electrode 30 is provided above the substrate support 14.The upper electrode 30 is supported on an upper portion of the chamberbody 12 through a member 32. The member 32 is formed of a materialhaving insulation properties. The upper electrode 30 and the member 32close the upper opening of the chamber body 12.

The upper electrode 30 may include a top plate 34 and a support 36. Thelower surface of the top plate 34 is a lower surface on the internalspace 10 s side and defines the internal space 10 s. The top plate 34may be formed of a low resistance conductor or semiconductor with lowJoule heat. A plurality of gas discharge holes 34 a are formed in thetop plate 34. The plurality of gas discharge holes 34 a penetrate thetop plate 34 in a plate thickness direction thereof.

The support 36 detachably supports the top plate 34. The support 36 isformed of a conductive material such as aluminum. A gas diffusionchamber 36 a is provided in the interior of the support 36. A pluralityof gas holes 36 b are formed in the support 36. The plurality of gasholes 36 b extend downward from the gas diffusion chamber 36 a. Theplurality of gas holes 36 b respectively communicate with the pluralityof gas discharge holes 34 a. A gas introduction port 36 c is formed inthe support 36. The gas introduction port 36 c is connected to the gasdiffusion chamber 36 a. A gas supply pipe 38 is connected to the gasintroduction port 36 c.

A gas source group 40 is connected to the gas supply pipe 38 through avalve group 41, a flow rate controller group 42, and a valve group 43.The gas source group 40 includes a plurality of gas sources. Each of thevalve group 41 and the valve group 43 includes a plurality of on-offvalves. The flow rate controller group 42 includes a plurality of flowrate controllers. Each of the plurality of flow rate controllers of theflow rate controller group 42 is a mass flow controller or a pressurecontrol type flow rate controller. Each of the plurality of gas sourcesof the gas source group 40 is connected to the gas supply pipe 38through a corresponding on-off valve of the valve group 41, acorresponding flow rate controller of the flow rate controller group 42,and a corresponding on-off valve of the valve group 43.

In the plasma processing apparatus 1, a shield 46 is detachably providedalong the inner wall surface of the chamber body 12. The shield 46 isalso provided on the outer periphery of the support 13. The shield 46prevents an etching byproduct from adhering to the chamber body 12. Theshield 46 is configured, for example, by forming a film having corrosionresistance on the surface of a member formed of aluminum. The filmhaving corrosion resistance may be a film formed of ceramic such asyttrium oxide.

A baffle plate 48 is provided between the support 13 and the side wallof the chamber body 12. The baffle plate 48 is configured, for example,by forming a film having corrosion resistance on the surface of a memberformed of aluminum. The film having corrosion resistance may be a filmformed of ceramic such as yttrium oxide. A plurality of through-holesare formed in the baffle plate 48. An exhaust port 12 e is providedbelow the baffle plate 48 and in the bottom portion of the chamber body12. An exhaust device 50 is connected to the exhaust port 12 e throughan exhaust pipe 52. The exhaust device 50 has a pressure adjusting valveand a vacuum pump such as a turbo molecular pump.

The plasma processing apparatus 1 further includes a radio frequencypower source 61. The radio frequency power source 61 is configured togenerate radio frequency power HF. The fundamental frequency of theradio frequency power HF is a frequency in a range of 13 MHz to 200 MHz,for example. The radio frequency power source 61 supplies the radiofrequency power HF to generate a plasma from the gas in the chamber 10.The radio frequency power source 61 is electrically connected to thelower electrode 18 through a matcher 62. The matcher 62 has a matchingcircuit. The matching circuit of the matcher 62 is configured to matchthe impedance on the load side (lower electrode side) of the radiofrequency power source 61 with the output impedance of the radiofrequency power source 61. A filter 63 may be provided between thematcher 62 and the lower electrode 18. The filter 63 is configured topass the radio frequency power HF and reduce or cut off other signalsdirected to the radio frequency power source 61. In another embodiment,the radio frequency power source 61 may be electrically connected to theupper electrode 30 through the matcher 62.

The plasma processing apparatus 1 further includes a bias power source81. The bias power source 81 is electrically connected to the lowerelectrode 18. The bias power source 81 is configured to generate biaspower BP to draw ions into the substrate support 14. The bias power BPis supplied to the lower electrode 18. A filter 83 may be providedbetween the bias power source 81 and the lower electrode 18. The filter83 is configured to pass the bias power BP and reduce or cut off othersignals directed to the bias power source 81.

Hereinafter, FIGS. 2 and 3 will be referred to together with FIG. 1.FIG. 2 is a diagram showing a configuration of a radio frequency powersource and a bias power source of a plasma processing apparatusaccording to an exemplary embodiment. FIG. 3 is an exemplary timingchart of radio frequency power (HF), ion density (Ni), an electrontemperature (Te), and bias power (pulsed negative direct-current voltageBV).

In an embodiment, the bias power source 81 is configured to periodicallygenerate a pulsed negative direct-current voltage BV as the bias powerBP with a cycle CP. The direct-current voltage BV is applied to thelower electrode 18. The repetition frequency of the pulsed negativedirect-current voltage BV, that is, the reciprocal of the cycle CP is afrequency in a range of 1 kHz to 800 kHz, for example.

In an embodiment, the bias power source 81 may include a direct-currentpower source 81 a and a switching element 81 b. The direct-current powersource 81 a is a direct-current power source that generates a negativedirect-current voltage. The direct-current power source 81 a may be avariable direct-current power source. The switching element 81 b isconnected between the direct-current power source 81 a and the lowerelectrode 18. If the switching element 81 b enters a conduction state,conduction is made between the direct-current power source 81 a and tothe lower electrode 18, so that a negative direct-current voltage isapplied to the lower electrode 18. On the other hand, if the switchingelement 81 b enters a non-conduction state, the direct-current powersource 81 a is electrically disconnected from the lower electrode 18, sothat the application of the negative direct-current voltage to the lowerelectrode 18 is stopped. Due to the state transition of the switchingelement 81 b, the pulsed negative direct-current voltage BV isgenerated. The conduction state and non-conduction state of theswitching element 81 b are controlled by a controller 80 (describedlater) or another controller.

The radio frequency power source 61 is configured to supply the radiofrequency power HF as one or more pulses PL in a first period P1. In thecase of the plasma processing apparatus 1, the first period P1 is aperiod in which the pulsed negative direct-current voltage BV is notapplied to the lower electrode 18. In the example shown in FIG. 3, onepulse PL of the radio frequency power HF is supplied in a single firstperiod P1.

The radio frequency power source 61 is configured to stop the supply ofthe radio frequency power HF in a second period P2. In the case of theplasma processing apparatus 1, the second period P2 is a period in whichthe pulsed negative direct-current voltage BV is applied to the lowerelectrode 18.

The radio frequency power source 61 generates the radio frequency powerHF such that each pulse PL has a power level that gradually increasesfrom the point in time of the start thereof to the point in time whenthe peak thereof appears. A rise time of each pulse PL of the radiofrequency power HF may be set to a time longer than the minimum risetime of the pulse of the radio frequency power that can be output fromthe radio frequency power source 61.

The ions in the plasma in the chamber 10 are accelerated toward thesubstrate W in the second period P2. As a result, the substrate W isetched in the second period P2. Therefore, in the second period P2, areaction product is released from the substrate W. In a case where theelectron temperature of the plasma is high, re-dissociation of thereaction product occurs in the plasma. The substance generated by there-dissociation of the reaction product may be deposited on thesubstrate W. In the plasma processing apparatus 1, since the radiofrequency power HF is not supplied in the second period P2, the electrontemperature of the plasma is low in the second period P2. Therefore,according to the plasma processing apparatus 1, the re-dissociation ofthe reaction product is suppressed. If the re-dissociation of thereaction product is suppressed, the formation of the deposit on thesubstrate W is suppressed. As a result, a reduction or clogging of anopening formed in the substrate W by plasma etching is suppressed.

Further, in the first period P1, the radio frequency power HF issupplied as one or more pulses PL. The power level of each pulse PLgradually increases to the peak thereof. Therefore, overshoot of theelectron temperature is suppressed. As a result, according to the plasmaprocessing apparatus 1, excessive dissociation of gas is suppressed.Therefore, according to the plasma processing apparatus 1, it becomespossible to etch the substrate W at a relatively high etching rate.

In an embodiment, as shown in FIG. 2, the radio frequency power source61 may include a power generator 61 g and an output 61 a. The powergenerator 61 g is configured to generate the radio frequency power HF.The output 61 a is configured to output the radio frequency power HFgenerated by the power generator 61 g. The output 61 a is electricallyconnected to the lower electrode 18 through the matcher 62.

FIG. 4A is a diagram showing an example of a waveform of combined powerof a plurality of power components, FIG. 4B is a diagram showing a powerspectrum of the combined power shown in FIG. 4A, and FIG. 4C is adiagram showing the waveform of the radio frequency power HF of anexample. As shown in FIG. 4C, the radio frequency power HF is pulsedradio frequency power which is supplied periodically. That is, the radiofrequency power HF includes the pulse PL that appears periodically.

In an embodiment, the radio frequency power HF includes a plurality ofpower components. The plurality of power components have a plurality offrequencies, respectively. As shown in FIG. 4B, the plurality offrequencies are set symmetrically with respect to a fundamentalfrequency f₀. The fundamental frequency f₀ is a frequency in a range of13 MHz to 200 MHz, for example. In an example, the fundamental frequencyf₀ is 40.68 MHz. Further, as shown in FIG. 4B, the plurality offrequencies are set at an interval of a predetermined frequency f_(P).In an embodiment, the frequency f_(P) is the reciprocal of the cycle CP.In the example shown in FIG. 4B, the respective frequencies of theplurality of power components are f₀−(3/2)×f_(P), f₀−f_(P)/2,f₀+f_(P)/2, and f₀+(3/2)×f_(P).

The envelope of the combined power of the plurality of power componentsincludes a plurality of peak groups, as shown in FIG. 4A. Each of theplurality of peak groups includes a plurality of peaks that appearperiodically. A plurality of peaks which are included in each of theplurality of peak groups periodically appear at a time interval T_(P).The time interval T_(P) is the reciprocal of the frequency f_(P).

As shown in FIG. 4C, the envelope of the radio frequency power HF has apeak that appears at the time interval T_(P). In an embodiment, theradio frequency power HF is composed of a peak group which includespeaks P_(M) having the maximum power level among the plurality of peakgroups. As shown in FIG. 4C, the radio frequency power HF is set suchthat the power level thereof is zero in periods P_(A). The periods P_(A)are periods excluding periods P_(P). The periods P_(P) are periods inwhich the peaks of the envelope of the radio frequency power HF appear,respectively. In an embodiment, the periods P_(P) are periods in whichpeaks P_(M) appear, respectively. Each of the periods P_(P) is a periodbetween a zero-cross region Z_(A) of the envelope immediately before thepoint in time when a corresponding peak of the envelope of the radiofrequency power HF appears and a zero-cross region Z_(B) of the envelopeimmediately after the point in time of the appearance. The zero-crossregion Z_(A) and the zero-cross region Z_(B) may be points in time atwhich the amplitude of the envelope of the radio frequency power HF hasa value that can be regarded as substantially zero. For example, each ofthe zero-cross region Z_(A) and the zero-cross region Z_(B) may be apoint in time at which the power level of the envelope has a power levelof 30% or less or 10% or less with respect to the power level of thepeak of the envelope of the radio frequency power HF.

As shown in FIG. 4C, each pulse of the radio frequency power HF has apower level that gradually increases to the peak thereof. Further, eachpulse has a power level that gradually decreases from the peak thereof.In the period P_(A) excluding the period P_(P) between the zero-crossregion Z_(A) immediately before each pulse and the zero-cross regionZ_(B) immediately after each pulse, that is, the period excluding theduration of each pulse, the power level of the radio frequency power HFis set to zero. The bandwidth of the radio frequency power HF is narrow.Therefore, according to the radio frequency power source 61 of anembodiment, it becomes possible to narrow the bandwidth of the pulsedradio frequency power HF. Therefore, according to the plasma processingapparatus 1, it becomes possible to suppress the reflected wave withrespect to the radio frequency power HF.

In an embodiment, the power generator 61 g may include a modulatedsignal generator 64, as shown in FIG. 2. In an embodiment, the powergenerator 61 g may further include an amplifier 65. The modulated signalgenerator 64 generates a modulated radio frequency signal. The radiofrequency power HF may be the modulated radio frequency signal which isgenerated by the modulated signal generator 64. In this case, theamplifier 65 is not necessary. Alternatively, the radio frequency powerHF may be generated by amplifying the modulated radio frequency signalby the amplifier 65.

In an embodiment, the modulated signal generator 64 includes a waveformdata generator 71, a quantizer 72, an inverse Fourier transformer 73,and a modulator 74. In an embodiment, the modulated signal generator 64may further include D/A converters 75 and 76 and low-pass filters 77 and78. The modulated signal generator 64 may be configured with, forexample, an FPGA (Field-Programmable Gate Array). Alternatively, themodulated signal generator 64 may be formed of several circuits.

The waveform data generator 71 generates waveform data corresponding tothe modulated radio frequency signal. The waveform data generator 71 isconfigured to acquire parameters (for example, a frequency, a phase, andthe like) for generating the waveform data from the input device andgenerate the waveform data by using the acquired parameters. Thewaveform data generator 71 outputs the generated waveform data to thequantizer 72.

The quantizer 72 is configured to quantize the waveform data generatedby the waveform data generator 71 to generate quantized data. Theinverse Fourier transformer 73 is configured to generate I data(in-phase component) and Q data (quadrature phase component) by applyinginverse Fourier transform to the quantized data. The I data and the Qdata are input to the modulator 74 via the D/A converters 75 and 76 andthe low-pass filters 77 and 78, respectively.

The modulator 74 is configured to generate a modulated radio frequencysignal by modulating two reference radio frequency signals of whichphases are different from each other by 90° by using the input I dataand Q data, respectively.

In an embodiment, the modulator 74 includes a PLL oscillator 74 a (PhaseLocked Loop Oscillator), a phase shifter 74 b, mixers 74 c and 74 d, anda synthesizer 74 e.

The PLL oscillator 74 a is configured to generate a reference radiofrequency signal. The reference radio frequency signal is input to themixer 74 c. Further, the reference radio frequency signal is input tothe phase shifter 74 b. The phase shifter 74 b is configured to generatea reference radio frequency signal having a phase that is different by90° from the phase of the reference radio frequency signal which isinput to the mixer 74 c. Specifically, the phase shifter 74 b isconfigured to shift the phase of the input reference radio frequencysignal by 90°. The reference radio frequency signal generated by thephase shifter 74 b is input to the mixer 74 d.

The mixer 74 c is configured to perform the multiplication of the inputreference radio frequency signal and the I data. The signal generated bythe multiplication of the mixer 74 c is input to the synthesizer 74 e.The mixer 74 d is configured to perform the multiplication of the inputreference radio frequency signal and the Q data. The signal generated bythe multiplication of the mixer 74 d is input to the synthesizer 74 e.The synthesizer 74 e is configured to add the signals input from themixer 74 c and the mixer 74 d to generate the modulated radio frequencysignal.

In an embodiment, the plasma processing apparatus 1 may further includethe controller 80. The controller 80 may be a computer which includes aprocessor, a storage unit such as a memory, an input device, a displaydevice, a signal input/output interface, and the like. The controller 80controls each part of the plasma processing apparatus 1. In thecontroller 80, an operator can perform a command input operation and thelike by using the input device in order to manage the plasma processingapparatus 1. Further, in the controller 80, the operating status of theplasma processing apparatus 1 can be visualized and displayed by thedisplay device. Further, a control program and recipe data are stored inthe storage unit of the controller 80. The control program is executedby the processor of the controller 80 in order to execute variousprocessing in the plasma processing apparatus 1. The processor of thecontroller 80 executes the control program and controls each part of theplasma processing apparatus 1 according to the recipe data, wherebyplasma processing is executed in the plasma processing apparatus 1.

In an embodiment, the controller 80 or another controller may controlthe phase of the bias power source 81 to set the phase of the cycle CPof the direct-current voltage By. According to this embodiment, itbecomes possible to adjust a time difference T1 (refer to FIG. 3)between the point in time of end of the supply of the pulse PL and thepoint in time of start of the application of the pulsed negativedirect-current voltage BV to the lower electrode 18. Therefore, it ispossible to adjust the electron temperature of the plasma before theapplication of the pulsed negative direct-current voltage BV to thelower electrode 18 is started.

More specifically, the controller 80 or another controller controls thebias power source 81 to set the phase of the negative direct-currentvoltage BV, that is, the supply start timing of the negativedirect-current voltage By. In an embodiment, the controller 80 oranother controller controls the timing at which the switching element 81b switches from the non-conduction state to the conduction state. Inthis way, the time difference T1 is controlled.

In an embodiment, the controller 80 or another controller may furthercontrol the bias power source 81 to set a duration length PW (FIG. 3) ofthe pulsed negative direct-current voltage By. In an embodiment, thecontroller 80 or another controller sets the duration length PW bycontrolling the length of a time when the switching element 81 bmaintains the conduction state. In this way, it becomes possible toadjust a time difference T2 (FIG. 3) between the point in time of end ofthe application of the pulsed negative direct-current voltage BV to thelower electrode 18 and the point in time of start of the supply of thepulse PL.

Hereinafter, FIGS. 5A, 5B, and 5C will be referred to. In anotherexample, as shown in FIG. 5B, the frequencies of the plurality of powercomponents of the radio frequency power HF are f₀−2×f_(P), f₀−f_(P), f₀,f₀+f_(P), and f₀+2×f_(P). In this example, as shown in FIG. 5A, theenvelope of the combined power of the plurality of power componentsincludes four peak groups. In this example, as shown in FIG. 5C, theradio frequency power HF is composed of a peak group which includes themaximum peaks among the four peak groups. It should be noted that theradio frequency power HF may be composed of two or more powercomponents. The respective frequencies of the two or more powercomponents are set symmetrically with respect to the fundamentalfrequency f₀ and are set at an interval which is defined by apredetermined frequency f_(P).

Hereinafter, a plasma processing apparatus according to anotherembodiment will be described with reference to FIGS. 6, 7, and 8. FIG. 6is a diagram schematically showing the plasma processing apparatusaccording to another exemplary embodiment. FIG. 7 is a diagram showing aconfiguration of a radio frequency power source and a bias power sourceof the plasma processing apparatus according to another exemplaryembodiment. FIG. 8 is another exemplary timing chart of the radiofrequency power (HF), the ion density (Ni), the electron temperature(Te), and the bias power (radio frequency bias power LF).

A plasma processing apparatus 1B according to another embodimentincludes a bias power source 81B and a filter 83B instead of the biaspower source 81 and the filter 83. The plasma processing apparatus 1Bfurther includes a matcher 82B. In other respects, the plasma processingapparatus 1B is configured in the same manner as the plasma processingapparatus 1.

The bias power source 81B is configured to generate the radio frequencybias power LF as the bias power BP for drawing ions into the substratesupport 14. The frequency of the radio frequency bias power LF is thereciprocal of the cycle CP. The frequency of the radio frequency biaspower LF is lower than the fundamental frequency f₀. The frequency ofthe radio frequency bias power LF is a frequency in a range of 400 kHzto 13.56 MHz, for example. In an example, the frequency of the radiofrequency bias power LF is 400 kHz. In an embodiment, the frequency ofthe radio frequency bias power LF may be the frequency f_(P) describedabove. The radio frequency bias power LF is supplied to the lowerelectrode 18.

The bias power source 81B is electrically connected to the lowerelectrode 18 through a matcher 82B. The matcher 82B has a matchingcircuit. The matching circuit of the matcher 82B is configured to matchthe impedance on the load side (lower electrode side) of the bias powersource 81B with the output impedance of the bias power source 81B. Afilter 83B may be provided between the matcher 82B and the lowerelectrode 18. The filter 83B is configured to pass the radio frequencybias power LF and reduce or cut off other signals directed to the biaspower source 81B.

As shown in FIG. 7, in an embodiment, the bias power source 81B mayinclude a signal generator 81Ba and an amplifier 81Bb. The signalgenerator 81Ba is configured to generate a radio frequency signal havingthe same frequency as the frequency of the radio frequency bias powerLF. The radio frequency signal generated by the signal generator 81Ba isinput to the amplifier 81Bb. The amplifier 81Bb is configured to amplifythe input radio frequency signal to generate the radio frequency biaspower LF.

In the plasma processing apparatus 1B, the radio frequency power source61 is configured to supply the radio frequency power HF as one or morepulses PL in the first period P1 in which the radio frequency bias powerLF which is output from the bias power source 81B has a positivevoltage, as shown in FIG. 8. In the example shown in FIG. 8, one pulsePL of the radio frequency power HF is supplied in a single first periodP1.

In the plasma processing apparatus 1B, the radio frequency power source61 is configured to stop the supply of the radio frequency power HF inthe second period P2 in which the radio frequency bias power LF which isoutput from the bias power source 81B has a negative voltage.

Also in the plasma processing apparatus 1B, similar to the plasmaprocessing apparatus 1, the radio frequency power source 61 generatesthe radio frequency power HF such that each pulse PL has a power levelthat gradually increases from the point in time of the start thereof tothe point in time when the peak thereof appears. Also in the plasmaprocessing apparatus 1B, similar to the plasma processing apparatus 1,the rise time of each pulse PL of the radio frequency power HF may beset to a time longer than the minimum rise time of the pulse of theradio frequency power that can be output from the radio frequency powersource 61.

The ions in the plasma in the chamber 10 are accelerated toward thesubstrate W in the second period P2. As a result, in the second periodP2, the substrate W is etched. Therefore, in the second period P2, areaction product is released from the substrate W. In a case where theelectron temperature of the plasma is high, re-dissociation of thereaction product occurs. The substance generated by the re-dissociationof the reaction product may be deposited on the substrate W. In theplasma processing apparatus 1B, since the radio frequency power HF isnot supplied in the second period P2, the electron temperature of theplasma is low in the second period P2. Therefore, according to theplasma processing apparatus 1B, the re-dissociation of the reactionproduct is suppressed. If the re-dissociation of the reaction product issuppressed, the formation of the deposit on the substrate W issuppressed. As a result, a reduction or clogging of an opening formed inthe substrate W by plasma etching is suppressed.

Further, in the first period P1, the radio frequency power HF issupplied as one or more pulses PL. The power level of each pulse PLgradually increases to the peak thereof. Therefore, overshoot of theelectron temperature is suppressed. As a result, according to the plasmaprocessing apparatus 1B, excessive dissociation of gas is suppressed.Therefore, according to the plasma processing apparatus 1B, it becomespossible to etch the substrate W at a relatively high etching rate.

In an embodiment, the controller 80 or another controller may controlthe bias power source 81B to set the phase of the radio frequency biaspower LF. Specifically, the radio frequency power source 61 and the biaspower source 81B are synchronized with each other by a clock signalwhich is provided from the controller 80 or another controller. Thecontroller 80 or another controller provides a signal for setting thephase of the radio frequency bias power LF to the bias power source 81Bto set the phase difference between the radio frequency power HF and theradio frequency bias power LF. The bias power source 81B outputs theradio frequency bias power LF with a given phase. According to thisembodiment, it becomes possible to adjust a time difference TA betweenthe point in time of end of the supply of the pulse PL and the point intime when the potential of the lower electrode 18 has a negative peak.Further, it becomes possible to adjust a time difference TB between thepoint in time when the potential of the lower electrode 18 has anegative peak and the point in time when the supply of the pulse PL isstarted.

Hereinafter, FIG. 9 will be referred to. FIG. 9 is still anotherexemplary timing chart of the radio frequency power (HF), the iondensity (Ni), the electron temperature (Te), and the bias power (pulsednegative direct-current voltage BV). As shown in FIG. 9, also in stillanother embodiment, the radio frequency power source 61 generates theradio frequency power HF such that each pulse PL has a power level thatgradually increases from the point in time of start thereof to the pointin time when the peak thereof appears. In still another embodiment, therise time of each pulse PL of the radio frequency power HF may be set toa time longer than the minimum rise time of the pulse of the radiofrequency power that can be output from the radio frequency power source61. In this embodiment, the radio frequency power source 61 may have aramp-up circuit or a ramp-up function for adjusting a rise time, thatis, a ramp rise time, of the rectangular pulse of the radio frequencypower. As shown in FIG. 9, in still another embodiment, a fall time ofeach pulse PL which is generated by the radio frequency power source 61may be shorter than the rise time of each pulse PL. For example, eachpulse may be switched from ON to OFF substantially instantaneously orcontinuously. Further, in the embodiment shown in FIG. 9, instead of thepulsed negative direct-current voltage BV, the radio frequency biaspower LF may be used as the bias power.

Hereinafter, FIG. 10 will be referred to. FIG. 10 is still anotherexemplary timing chart of the radio frequency power (HF) and the biaspower (pulsed negative direct-current voltage BV). In still anotherembodiment, as shown in FIG. 10, the radio frequency power source 61 maygenerate a plurality of pulses PL for generating a plasma in the firstperiod P1. In the first period P1, the plurality of pulses PL aresupplied continuously or intermittently and sequentially. According tothis embodiment, the average value of the electron temperature of theplasma in the first period P1 is reduced. Therefore, excessivedissociation of gas in the chamber 10 is further suppressed. In theembodiment shown in FIG. 10, instead of the pulsed negativedirect-current voltage BV, the radio frequency bias power LF may be usedas the bias power.

Hereinafter, FIG. 11 will be referred to. FIG. 11 is a diagram showingthe configuration of a radio frequency power source according to anotherexemplary embodiment. As shown in FIG. 11, in another embodiment,instead of the radio frequency power source 61, a radio frequency powersource 61B may be used. The radio frequency power source 61B includes apower generator 61Bg and an output 61 a. The power generator 61Bg isconfigured to generate the radio frequency power HF. In the radiofrequency power source 61B, the output 61 a is configured to output theradio frequency power HF generated by the power generator 61Bg.

The power generator 61Bg has a modulated signal generator 64B. The powergenerator 61Bg may further include the amplifier 65. The modulatedsignal generator 64B generates a modulated radio frequency signal. Theradio frequency power HF may be the modulated radio frequency signalwhich is generated by the modulated signal generator 64B. In this case,the amplifier 65 is not necessary. Alternatively, the radio frequencypower HF may be generated by amplifying the modulated radio frequencysignal by the amplifier 65.

The modulated signal generator 64B may include a plurality of signalgenerators 911 to 91N, an adder 92, and a switching circuit 93. Here,“N” is an integer of 2 or more. The plurality of signal generators 911to 91N are configured to generate a plurality of radio frequencysignals, respectively. The respective frequencies of the plurality ofradio frequency signals are set symmetrically with respect to thefundamental frequency f₀. The respective frequencies of the plurality ofradio frequency signals are set at the interval of the predeterminedfrequency f_(P).

The adder 92 is configured to add the plurality of radio frequencysignals from the plurality of signal generators 911 to 91N to generate acomposite signal. The envelope of the composite signal has peaks thatperiodically appear at the time interval T_(P). The switching circuit 93is configured to generate the modulated radio frequency signal from thecomposite signal. The modulated radio frequency signal is set such thatthe amplitude level thereof is zero in the period P_(A) excluding theperiod P_(P) between the zero-cross region Z_(A) of the envelopeimmediately before the point in time of appearance of each peak of theenvelope of the composite signal and the zero-cross region Z_(B) of theenvelope immediately after the point in time of the appearance. Theradio frequency power source 61B is also able to generate the radiofrequency power HF, similarly to the radio frequency power source 61.That is, the radio frequency power source 61B is also able to generatepulses of the radio frequency power.

While various exemplary embodiments have been described above, variousadditions, omissions, substitutions and changes may be made withoutbeing limited to the exemplary embodiments described above. Elements ofthe different embodiments may be combined to form another embodiment.

In another embodiment, the plasma processing apparatus may be anothertype of plasma processing apparatus such as an inductively coupledplasma processing apparatus. In the inductively coupled plasmaprocessing apparatus, the radio frequency power HF is supplied to anantenna for generating an inductively coupled plasma.

From the foregoing description, it will be appreciated that variousembodiments of the present disclosure have been described herein forpurposes of illustration, and that various modifications may be madewithout departing from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A plasma processing apparatus comprising: aplasma processing chamber; a lower electrode provided in the plasmaprocessing chamber; an upper electrode provided above the lowerelectrode; a bias power source coupled to the lower electrode andconfigured to generate a negative direct-current voltage, the bias powersource being configured to stop application of the negativedirect-current voltage to the lower electrode in a first period and toapply the negative direct-current voltage to the lower electrode in asecond period, wherein the first period and the second period arealternatively repeated; and a radio frequency power source coupled tothe upper electrode or the lower electrode and configured to generateone or more pulses of radio frequency power in the first period, whereineach of the one or more pulses has a start period in which a power levelthereof gradually increases from a point in time of start thereof. 2.The plasma processing apparatus according to claim 1, further comprisinga controller configured to control the bias power source to set a phaseof a cycle which includes the first period and the second period.
 3. Theplasma processing apparatus according to claim 2, wherein the controlleris configured to further control the bias power source to set a durationlength of the negative direct-current voltage in the cycle.
 4. Theplasma processing apparatus according to claim 1, wherein a rise time ofeach of the one or more pulses is longer than a minimum rise time of apulse of radio frequency power capable of being output from the radiofrequency power source.
 5. The plasma processing apparatus according toclaim 1, wherein the radio frequency power source is configured to becapable of adjusting a rise time of each of the one or more pulses. 6.The plasma processing apparatus according to claim 1, wherein the radiofrequency power source is configured to sequentially supply a pluralityof pulses as the one or more pulses in the first period.
 7. The plasmaprocessing apparatus according to claim 1, wherein the radio frequencypower source is coupled to the lower electrode.
 8. The plasma processingapparatus according to claim 1, wherein the radio frequency power has afrequency which is not less than 13 MHz and not more than 200 MHz. 9.The plasma processing apparatus according to claim 1, wherein the radiofrequency power source is configured to stop supply of the radiofrequency power in the second period.
 10. A plasma processing apparatuscomprising: a plasma processing chamber; a lower electrode provided inthe plasma processing chamber; an upper electrode provided above thelower electrode; a bias power source coupled to the lower electrode andconfigured to generate radio frequency bias power which has a continuouswave form of which a frequency is a first frequency, wherein each cycledefined by the first frequency includes a first period and a secondperiod, a voltage of the radio frequency bias power in the first periodis higher than an average voltage of the radio frequency bias power, anda voltage of the radio frequency bias power in the second period islower than an average voltage of the radio frequency bias power; and aradio frequency power source coupled to the upper electrode or the lowerelectrode and configured to generate one or more pulses of radiofrequency power in the first period, the radio frequency power having asecond frequency which is higher than the first frequency, wherein eachof the one or more pulses has a start period in which a power levelthereof gradually increases from a point in time of start thereof. 11.The plasma processing apparatus according to claim 10, furthercomprising a controller configured to control the bias power source toset a phase of the radio frequency bias power.
 12. The plasma processingapparatus according to claim 10, wherein a rise time of each of the oneor more pulses is longer than a minimum rise time of a pulse of radiofrequency power capable of being output from the radio frequency powersource.
 13. The plasma processing apparatus according to claim 10,wherein the radio frequency power source includes a power generatorconfigured to generate the radio frequency power, and an outputconfigured to output the radio frequency power generated by the powergenerator.
 14. The plasma processing apparatus according to claim 13,wherein the power generator is configured to generate the radiofrequency power including a plurality of power components respectivelyhaving a plurality of frequencies, the plurality of frequencies beingset symmetrically with respect to a fundamental frequency at an intervalof a predetermined frequency, an envelope of the radio frequency powerhaving peaks that periodically appear at a time interval defined by thepredetermined frequency or a frequency that is a multiple of twice ormore the predetermined frequency, and a power level of the radiofrequency power being set to be zero in a period excluding a periodbetween a zero-cross region of the envelope immediately before a pointin time of appearance of each of the peaks and a zero-cross region ofthe envelope immediately after the point in time of the appearance. 15.The plasma processing apparatus according to claim 13, wherein the powergenerator includes: a waveform data generator; a quantizer configured toquantize waveform data generated by the waveform data generator togenerate quantized data; an inverse Fourier transformer configured togenerate I data and Q data by applying inverse Fourier transform to thequantized data; and a modulator configured to generate a modulated radiofrequency signal by modulating two reference radio frequency signals ofwhich phases are different from each other by 90° by using the I dataand the Q data, and the power generator is configured to generate theradio frequency power from the modulated radio frequency signal.
 16. Theplasma processing apparatus according to claim 10, wherein the radiofrequency power source is configured to be capable of adjusting a risetime of each of the one or more pulses.
 17. The plasma processingapparatus according to claim 10, wherein the radio frequency powersource is configured to sequentially supply a plurality of pulses as theone or more pulses in the first period.
 18. The plasma processingapparatus according to claim 10, wherein the radio frequency powersource is coupled to the lower electrode.
 19. The plasma processingapparatus according to claim 10, wherein the second frequency is notless than 13 MHz and not more than 200 MHz.
 20. The plasma processingapparatus according to claim 10, wherein the radio frequency powersource is configured to stop supply of the radio frequency power in thesecond period.